Portable computer with low-power audio CD-player

ABSTRACT

A system and method to reduce power consumption in a portable computer system while allowing the CDROM drive to continue playing audio CDs. When the system enters a suspend mode, the status of the CDROM drive is checked, and if it is playing an audio CD, it remains powered, otherwise power to the CDROM drive is also suspended. The system recognizes when the audio CD is finished playing and then places the CDROM drive into the suspend mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 09/150,530, filed Sep.10, 1998, which is a continuation of Ser. No. 08/699,989, filed Aug. 20,1996 (now U.S. Pat. No. 5,838,983. issued Nov. 17, 1998) and also claimspriority from provisional No. 60/019,109, filed Jun. 3, 1996, all ofwhich are hereby incorporated by reference. However, the content of thepresent application is not necessarily identical to that of the priorityapplication.

BACKGROUND AND SUMMARY OF THE INVENTION

Multimedia PCs often incorporate CD-ROM drives and audio subsections.CD-ROM players are valuable as data storage devices, but also may beused to play standard Audio CD disks. However, typical computers todayrequire that the CPU be fully “on” to play an audio CD. As a result, atypical portable computer today can only play CDs for about 2-3 hours.

Operation of the Portable CD-ROM and Audio Subsection Today

Portable computers today are typically organized as a system including aMicroprocessor and its support chips, as well as common peripherals(including, e.g., the graphics subsection, PCMCIA controller, hard diskand floppy disk controller, interface port control, such as for printerand serial busses, for example, keyboard controller, etc.) whichinterface to the CPU. A fixed disk drive and CD-ROM are typicallyattached on a common bus, such as an IDE or SCSI bus. “ATAPI-compliant”CD-ROMs are capable of either data retrieval, or playing audio disks (socalled “Redbook” or “CD-A” disks). The CD-ROM control signals and datacome over the common bus, but audio signals are output directly from theCD-ROM on an independent analog output.

A typical example of a computer audio system employs an audio mixer or“SoundBlaster” compatible audio codec. The output of the CD-ROM is acommon input to the Audio Mixer. The function of the mixer is to providevolume control of the CD-ROM outputs along with other PC sounds. Theoutput of the mixer goes to a power amplifier, which outputs to speakersor to a headphone jack. The audio codec and power amplifier togetherform the Audio section of the computer.

A Real Time Clock (RTC) is a virtually universal peripheral to today'sPCs. The RTC is always powered up, and is used to both keep track of thetime and date and to act as an “alarm clock” to the system, whereby thesystem may be “woken” from Suspend after a predetermined time haspassed.

Power management circuitry is an integral part of a typicalbattery-powered computer. Power management is principally controlled bya program in the CPU memory and enables active status to the peripheralsand support logic of the system.

Typically, a low-power “Suspend” mode is supported, where the entirestate of the system is frozen, timing clocks are turned off, and poweris removed from any logic whose state is unimportant. Power to at leastsome portions of the system must remain active during Suspend. Thefunction of Suspend mode is to freeze the condition of the system whiletaking the least amount of power. In Suspend, the only activity thesystem supports is to recognize a “wakeup” event and return to normaloperation: the “RESUME” sequence may be initiated by the system (e.g. bybutton press, modem ring, Real time clock alarm, or low battery event).

Typical power dissipation for the unit in a FULL SUSPEND mode is about200 milliwatts. After “Resume” from Suspend, power to all devices isreturned, and the pre-existing states of the CPU, the operating system,and the application is restored to its state before Suspend wasexecuted.

Suspend mode is usually entered after a period of inactivity, after acritical condition event (for instance, a low battery condition orovertemperature of the unit), or manually by the user.

Typically, when in Suspend mode, power to the fixed disk and CD-ROMdrives are disconnected (shown here as SW1 under the control of aSUSPEND status signal). The audio subsection is also placed into anon-functional mode; either power may be removed completely from thesystem or the Audio mixer/Codec and power amplifier may be placed into anon-functional SUSPEND mode under the control of the SUSPEND statusline.

The peripheral components are also placed into inactive functionality orturned off by the single SUSPEND status.

Applications run within the CPU to play an audio CD. For example, withinthe Windows operating system, these utilities are called “Media Player”or “CD player,” though many such applications are known.

Limitation of Known Implementations

For the sole purpose of playing an Audio CD, today's portable computeruses more power than is required. This is because, in order to play anAudio Compact Disk today, the entire peripheral set remains powered andfunctional, although they are not being used. Since a full SUSPENDglobally powers down all peripherals, it is not possible on today'sportable computers to allow the system to suspend all unnecessary systemelements while playing an audio CD.

Innovative System and Method for Low-Power CD Audio

The present application describes a computer system and method whichprovides a “CD-player Suspend” mode, where the audio section and CD-ROMare left active while the remaining system is placed into a low powermode.

BRIEF DESCRIPTION OF THE DRAWING

The disclosed inventions will be described with reference to theaccompanying drawings, which show important sample embodiments of theinvention and which are incorporated in the specification hereof byreference, wherein:

FIG. 1 shows a typical prior art computer system capable of entering asuspend mode.

FIG. 2 is a computer system constructed according to the preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment (by way of example, and not of limitation), in which:Portable computers today are typically organized as shown in FIG. 1.

The “System” consists of a CPU 1; here, the CPU refers to theMicroprocessor and support chips themselves. The common peripherals 8(including, e.g., the graphics subsection, PCMCIA controller, hard diskand floppy disk controller, interface port control (printer and serialbusses), keyboard controller, etc.) interface to the CPU.

A fixed disk drive 2 and CD-ROM 3 are typically attached on a commonbus, in this case an IDE or SCSI bus. “ATAPI-compliant” CD-ROMs arecapable of either data retrieval, or playing audio disks (so called“Redbook” or “CD-A” disks). The CD-ROM control signals and data comeover the IDE bus, but audio signals are output directly from the CD-ROMon an independent analog output.

A typical example of a computer audio system employs an audio mixer or“SoundBlaster” compatible audio codec 4. The output of the CD-ROM is acommon input to the Audio Mixer. The function of the mixer is to providevolume control of the CD-ROM outputs along with other PC sounds. Theoutput of the mixer goes to a power amplifier 5. Final output of thepower amp is to speakers or to a headphone jack. The audio codec andpower amplifier together comprise the Audio section of the computer.

A Real Time Clock (RTC) 6 is a universal peripheral to the PC. The RTCis always powered up, and is used to both keep track of the time anddate and to act as an “alarm clock” to the system, whereby the systemwill be “woken” from Suspend after a predetermined time has passed.

Power management circuitry 7 is an integral part of the battery-poweredcomputer. Power management is principally controlled by a program in theCPU memory and enables active status to the peripherals and supportlogic of the System.

This application describes a method and system for enabling a low powerAudio CD player mode, where the CPU is put into Suspend and the Audio CDis allowed to play. Without this mode, a typical portable computer couldonly play CDs for about 2-3 hours; with this mode, performance of 10-15hours on a battery charge is possible. The convenience is for mobileusers who want to enjoy the performance of a standalone “Diskman” butdon't want the carry weight and size of a separate player.

The basic operation for the presently preferred embodiment is tointerrogate the status of the CD-ROM when a Suspend is initiated, anddecide which of two low power states to configure the CD-ROM drive andthe audio subsection to. The preferred embodiments include a system andmethod to separate “global” Suspend (whereby all peripherals are turnedoff) from the “CD-player” Suspend.

A. The hardware required for the presently preferred embodiment is notaltogether unique but requires a certain minimum of functionality;

i. As with the traditional portable, the processor and peripheral set(graphics subsystem, processor and supporting chipset, keyboardcontroller, peripheral controller, etc) can be placed into a low-powerSUSPEND mode.

ii. One important feature of the preferred embodiment is the ability toleave the Audio mixer portion of the Codec and the power amplifiers inan active state independent of the state of the peripherals orprocessor. In this state the output of the CD-ROM audio channel may beoutput through the codec and amplifiers.

iii. Another important feature of this embodiment is the ability toleave the CD-ROM active when playing an audio CD, independent of theSuspend status of the peripherals and processor.

iv. Another feature of this embodiment is the ability to remove powerfrom the Fixed disk while leaving power to the CD-ROM (allowing theCD-ROM to remain active). There are several standard ways (and oneunique way) to accomplish this. In one alternative, the Fixed disk drivemay be placed into a low power Suspend condition independent of theCD-ROM.

v. Optionally, a signalling method for Audio CD commands (for example,fast forward, seek, skip) from the keyboard or control panel may becomeactive when the unit is in a “CD Player Suspend” mode.

B. Logic is called during the system entrance into Suspend. The purposeof this logic is to;

i. Interrogate the system to find if an audio CD is playing in theCD-ROM drive. This interrogation may be manual or automatic.

ii. As with traditional portables, configure the processor and allperipherals to lowest power mode (“Full Suspend”) if no audio disk isplaying in the CD-ROM.

iii. (Unique to this invention) to configure the processor andperipherals to lowest power mode while allowing the CD-ROM drive andAudio subsection to remain active if an Audio CD disk is playing.

C. One feature of the preferred embodiment is a method to exit the lowpower “CD-player Suspend” once the audio CD is finished playing andconfigure the machine to an Active state, to a “Full Suspend” state, orto an “Off” state.

A. Specific Hardware Implementation

FIG. 2 shows a specific Hardware implementation of the low power CDplayer.

11. Section 11 comprises the CPU and its support chips. In thisinstance, the processor is a Pentium CPU and the support chips are theOpti 558 family (556, 557, 558, and 602 devices). A general purposeoutput of the 602 chip is set high by the CPU when a SUSPEND operationis to occur. Another general purpose output controls the new function,AUDIO_SUSPEND. Both outputs are under control of the CPU via writes toI/O register locations across the ISA bus.

12. The Fixed Disk drive 12 is connected to the IDE bus. The power tothe fixed disk drive is enabled through a transistor which is turned OFFwhen Suspend is active. This switch is represented at SW1.

13. The CD-ROM 13 has separate power control, enabled through SW3. SW3is a transistor which is turned off when the signal AUDIO_SUSPEND fromsection 11 is active.

14. The audio mixer and codec functions are performed with an ESS1688device 14. The ESS1688 is a single-chip SoundBlaster-compatible devicewhich interfaces to the CPU across an ISA bus. The ESS1688 device may beplaced into “partial standby,” where the digital section (the Codecfunction of the ESS) is placed into suspend but the analog mixer sectionremains active. This enables the ESS device to continue to function as avolume control when the System is in CD-player Suspend mode. The ESS1688device is placed into a partial standby mode by writes across the ISAbus to registers inside the device. Power is applied to the ESS1688device during both SUSPEND or CD-Player Suspend modes. The specificationfor the ESS1688 may be obtained from ESS Technology, Inc., 48107 LandingParkway, Fremont, Calif 94538-6407, USA, and is hereby incorporated byreference.

15. Power to the audio amplifiers 15 is enabled through a transistorgated by AUDIO_SUSPEND.

16. The Real Time Clock 16 (RTC) function is performed by the 602 chip.The RTC functions are always active. In this specific implementation,the RTC is used to terminate the CD-player mode by waking the systemafter the audio CD will have finished playing.

17. Power management circuitry 17 is an integral part of thebattery-powered computer. Power management is principally controlled bya program in the CPU memory and enables active status to the peripheralsand support logic of the System.

18. The peripheral chips 18 (the graphics controller, fixed disk drivelogic, parallel and serial port controls, etc) is powered off bydisabling a transistor connected to VCC. (In usual practice, theregister contents of these peripherals will be read and stored intonon-volatile memory under control by the CPU before power is removed).The transistor is turned off when the signal SUSPEND is active.

19. Because the CD-ROM drive 13 shares the IDE bus with the Fixed diskdrive 12, and power is removed from the Fixed disk drive, the controllines attached to the IDE device will go low. Since the CD-ROM controllines are active low, this would force the CD-ROM into an active stateand upset the state of the CD-ROM. To avoid this, the control lines tothe CD-ROM must be forced into a non-active state. In the preferredembodiment, this function is performed by isolating the control lines tothe CD-ROM with a tristatable buffer 19 gated by AUDIO_SUSPEND. Thelines which are tristated include the RESET*, WRITE*, and READ*. TheCD-ROM control lines are held inactive through the use of pullupresistors added between the CD-ROM inputs and VCC.

B. A Method to Enter and Exit CD-Player Mode

This process is performed when a SUSPEND is requested. According to thepreferred method; the system interrogates whether the CD-ROM is playingan Audio CD and determines the appropriate power state of the system.The system then enables a mechanism for terminating the CD-Playersuspend mode and returns the system to a Full Suspend mode. As is usualfor any SUSPEND function, the software for performing these functions isstored in BIOS ROM accessible by the CPU.

1. Interrogating the CD-ROM

Characteristic of an ATAPI compliant CD-ROM is the command “Play AudioCD.” This command will be issued by an application, for example the“Media Player” application under the Windows operating system. Afterthis command is issued, the CD-ROM will play without any furtherinstruction by the CPU.

In the preferred embodiment, the system determines if the CD-ROM isplaying an Audio CD through an ATAPI query to the CD-ROM drive.Available, standard ATAPI commands include the REQUEST SENSE, INQUIRE,and READ CD commands. The CD-ROM will respond with a status byteindicating if an Audio CD is busy playing.

2. No Audio CD is Playing

If no audio CD is playing (an ATAPI query answer replies negatively)then the entire system is placed into Full SUSPEND. The system performsnormal SUSPEND function (copies all important register data tonon-volatile memory and enables a Resume event) before concluding withthe below power sequence;

a. The ESS1688 is put into Full Suspend. Full suspend is entered bysetting bit 3 of the Power management register (register 227h) to a “0”(“ANALOG stays off” ); then by pulsing bit 2 high, then low.

b. Power to the CD-ROM and to the power Amplifiers is turned off bysetting the line AUDIO_SUSPEND active.

c. Power is removed from the remaining chipset (and main functionalclocks are terminated) by setting the SUSPEND line active.

3. An Audio CD is Playing

If an Audio CD is playing (ATAPI query returns “Playing Audio CD”status) then the CD-ROM drive and Audio are left active while the restof the system is placed into Suspend.

After copying the state of the peripheral set registers to non-volatilememory (the normal operation before executing a full Suspend) the systemperforms the following timing sequence;

a. The ESS1688 is placed into “partial suspend.” Partial suspend isentered by setting bit 3 of the Power control register to a “1,” then bypulsing bit 2 high, then low.

b. Power to the CD-ROM is left to the CD-ROM, and to the poweramplifiers by leaving the signal “CD-player Suspend” line inactive.

c. A mechanism is employed to terminate the CD-player mode and return tothe Full Suspend mode when the CD is through playing. This mechanismuses the RTC device to periodically wake the System from “CD-playerSuspend” to “Full awake” condition. This is accomplished by;

i. the RTC has an alarm feature. When the actual time matches a presettime, an “alarm” is issued. The alarm is activated by reading thepresent time, adding a certain amount to the time, then writing to theAlarm register inside the RTC. In this example, 15 minutes is added tothe actual time to create the Alarm time (the alarm will ring 15 minuteslater). The alarm registers are indexes 01h, 03h, and 05h inside the RTCI/O location of 70h and 71h.

ii. The alarm is enabled to wakeup the System by setting the IRQ *inthis case, ISA IRQ8 from the RTC) to generate a “RESUME” event. This isdone by writing to the register SYSCFG 6Ah, bit 6 inside the 602 chip.

d. The system enters an otherwise “full” suspend by setting the Suspendline active. The CPU (1), peripheral set (8), and hard drive (2) willbecome inactive and the isolation to the CD-ROM (9) will become active.The state of the CD-ROM is thus preserved, and the power amplifiers willcontinue to operate in the “CD-Player” suspend mode.

e. A mechanism checks to see if the Audio CD is finished playing. 15minutes after the System enters CD-player suspend mode, the RTC willissue an IRQ and the system will RESUME. Normally upon a resume, a fullrestoration is made to the system and the peripheral set. For thepreferred embodiment, a limited RESUME occurs, where the only task forthe processor is to query the CD-ROM for playing status and the systemrepeats the entire process (at 1 above) . If the CD-ROM has stoppedplaying the audio CD, a query to the CD-drive will return the status“Audio disk stopped.” In that case (no audio CD is playing) the systemwill enter at “2” and issue a full Suspend. If the Audio CD is playing,the system continues at “3” and the Audio CD continues playing.

According to one disclosed embodiment, there is provided a method foroperating a portable computer system, comprising the steps of: receivinga command to place said system in a suspend mode; determining whether anaudio CD is playing in a CDROM drive; if an audio CD is not playing,placing said system in a suspend mode; if an audio CD is playing,continuing to operate said CDROM drive, while placing the remainder ofsaid system in a suspend mode.

According to another disclosed embodiment, there is provided a methodfor operating a portable computer system, comprising the steps of:receiving a command to place said system in a suspend mode; determiningwhether an audio CD is playing in a CDROM drive; if an audio CD isplaying, then leaving said CDROM drive in its present state; isolatingat least one of a plurality of CDROM control signals from other systemsignals; placing a digital section of an audio CODEC in a suspend mode;leaving an analog section of said audio CODEC in an active mode; andleaving at least one audio power amplifier in an active state; if anaudio CD is not playing, then placing said CDROM drive in a suspendmode; placing said audio and digital sections of said CODEC in a suspendmode; placing said audio power amplifier in a suspend mode.

According to another disclosed embodiment, there is provided a portablecomputer system comprising: a microprocessor; a memory connected to saidmicroprocessor; a display device connected to display data generated bysaid microprocessor; an audio controller connected to saidmicroprocessor; an audio input device connected to said audio controllerfor reading audio data; a battery connected to power saidmicroprocessor, memory, display device, audio controller, and audioinput device; wherein said system may be placed in a suspend mode inwhich said microprocessor and display are placed reduced power state;and wherein said audio input device and said audio controller may beselectably placed in a reduced power state when said system is in saidsuspend mode.

Further Modifications and Variations

As will be recognized by those skilled in the art, the innovativeconcepts described in the present application can be modified and variedover a tremendous range of applications, and accordingly the scope ofpatented subject matter is not limited by any of the specific exemplaryteachings given.

Variations of the CD-ROM isolation logic 9

The preferred approach isolates the CD-ROM from the IDE bus when the lowpower CD-Player suspend mode is enabled. There are other methods foraccomplishing this;

1. No isolation is used between the Fixed disk drive and the CD-ROM.There are 2 variations of this method;

a. The hard drive and CD-rom drive may be powered at the same time; noeffort is made to isolate the CD-rom power from the hard drive power.The fixed disk may be placed in to a SUSPEND mode by writing to acontrol register in the Fixed disk itself. Because the Fixed Disk driveis powered up in this mode, it will not activate the (active low)control signals on its attached IDE bus as it would if powered off. Thisis not the preferred approach, since today the fixed disk drive consumesabout half a watt when in SUSPEND (about 20% of the CD-Player suspendpower budget).

b. The hard drive logic may be “input tolerant” so that when the harddrive is unpowered, there is no conduction between the IDE bus and thehard drive. No such drives exist today.

2. Isolation may be used on the hard drive; instead of decoupling theIDE bus from the CD-rom drive during CD-Player mode, the hard drive maybe decoupled and powered off. This requires the IDE interface logic tomaintain an inactive state during the CD-Player Suspend.

3. Isolation may consist of a latch instead of a tristatable buffer(section 9) since the purpose of the isolation is simply to maintain thepresent state of the CD-ROM.

4. The CD-ROM may remain powered during either Full SUSPEND or CD-PLAYERSUSPEND, but have the CD-ROM enter a low-power Suspend condition insteadof being powered off when no audio CD is playing.

Variations in the Audio Mixer

The audio mixer could be bypassed completely in CD-Player mode. Volumecontrol could be done by other passive or active circuitry. In thepreferred approach, volume control is performed simply with apotentiometer located between the Audio Mixer and the power amplifier.

Variations in Termination of CD-Player mode

The preferred approach uses the RTC to wakeup the system periodicallyand re-evaluate the status of the CD-ROM. Other approaches may be used;

1. The RTC may be set for a single maximum time before the CD-Playermode is exited. The time may be the maximum possible length of an audioCD (74 minutes) or the system may determine the playing time remainingon the present CD and set the RTC alarm for that length of time.

2. The System could wake up upon an opening of the CD-drive tray. Thiswould be more convenient to a user who wants to start playing anotherdisk, since the application to initiate playing of the next CD would beavailable through the operating system. One possible implementation forthis is to have the IRQ on the IDE bus wake the system from CD-PLAYERSUSPEND to Fully active, where the application which initiates theCD-player function could restart.

3. The CD-Rom drive could accept commands from another control sourcewhen in CD-Player suspend for common Disk player commands such as trackskip, fast forward reverse, etc. In this variation, control buttonswhich are read by the System during Fully On operation but are read bythe CD-ROM when in CD-Player mode. A possible implementation for thisis;

1. On the system enclosure are dedicated lines for the CD-rom commands.During normal (fully ON) operation, these lines are read by the keyboardcontroller and instruct an audio disk player application running underthe operating system. The Application itself instructs the CD_ROM tochange tracks, etc by issuing ATAPI packet commands to the CD-ROM.

2. During CD-Player mode, the buttons are read directly by the CD-ROMwith no required intervention by the CPU. A possible implementation ofthis is to change the function of the IDE bus to signal the CD-ROM drivethat the CD-Player mode is engaged, and to signal directly to the CD-ROM(not through the packet ATAPI commands) entrance to CD-player mode, theCD is alerted to use the alternative control lines instead of ATAPIcommands.

Variation on the Method

The preferred approach interrogates the ATAPI CD-ROM by query commandsto detect the playing status of the CD. Other methods exist to determineif a CD is playing an Audio Disk;

1. Another method for determining if an audio CD is playing is for theapplication which initiates the CD-rom playing the Audio disk to“register” with the system when a play is initiated. Instead of thesystem reading the state of the CD-ROM drive, it can instead read simplya memory bit which is set by the application itself.

2. The system can monitor the audio output stream of the audio mixer todetermine if a CD-ROM is active. In this implementation, the systemwould measure the analog output of the CD-ROM to determine the status ofthe CD-ROM drive. The system could also use this to detect when an AudioCD is finished playing and terminate the CD-Player mode.

3. An activity line from the CD-ROM itself could indicate that theCD-ROM is busy playing an audio CD. A possible implementation is for theAudio CD-rom to hold its DASP* line, Interrupt line, or Activity LEDactive during Audio CD play. The DASP* line is commonly used to indicatedata read activity from a CD-ROM drive, but usually does not becomeactive today during play of an Audio CD. So such an implementation wouldrequire an enhancement of the current ATAPI CD-ROM drive.

It should also be noted that the disclosed innovative ideas are notlimited only to Windows, DOS or UNIX systems, but can also beimplemented in other operating systems.

It should also be noted that the disclosed innovative ideas are notlimited only to systems using ISA, EISA, and/or PCI busses, but can alsobe implemented in systems using other bus architectures.

It should also be noted that the disclosed innovative ideas are notlimited only to systems based on an x86-compatible microprocessor, butcan also be implemented in systems using 680x0, RISC, or other processorarchitectures.

It should also be noted that the disclosed innovative ideas are not byany means limited to systems using a single-processor CPU, but can alsobe implemented in computers using multiprocessor architectures.

What is claimed is:
 1. A method of operating a portable computer systemthat includes an audio subsystem and a peripheral drive, comprising thesteps of: placing said portable computer system in a low-power state,while the audio subsystem and the peripheral drive remain in a normalpower mode; and operating said audio subsystem and said peripheral drivewhile said portable computer system is in the low-power state.
 2. Amethod as in claim 1, wherein said peripheral drive comprises a CD-ROMdrive capable of receiving an audio CD-ROM, and said CD-ROM drive andsaid audio subsystem are capable of remaining powered to play an audioCD-ROM when the portable computer system is in the low-power state.
 3. Amethod as in claim 1, further comprising the steps of: determining whenthe CD-ROM drive is no longer playing an audio CD-ROM; and placing saidCD-ROM drive and said audio subsystem in a low-power state.
 4. A methodas in claim 2, wherein said audio subsystem includes a power amplifier.5. A method as in claim 4, further comprising the steps of: determiningwhen the CD-ROM drive is no longer playing an audio CD-ROM; and placingsaid CD-ROM drive and said power amplifier in a low-power state.
 6. Amethod as in claim 1, wherein said audio subsystem includes an audiomixer.
 7. A method as in claim 3, wherein said audio subsystem includesan audio mixer and codec, and the audio mixer remains powered when anaudio CD-ROM is playing in the CD-ROM drive, and the codec is placed ina low-power state together with the portable computer system.
 8. Amethod as in claim 7, wherein the audio subsystem includes a poweramplifier that remains powered when an audio CD-ROM is playing in theCD-ROM drive.
 9. A method as in claim 1, further comprising the step ofturning off power to the peripheral drive and to said audio subsystemwhen no audio medium is playing in said peripheral drive.
 10. A methodas in claim 1, wherein the low-power state comprises a suspend mode. 11.A method as in claim 2, wherein said CD-ROM is electrically isolatedfrom said portable computer system.
 12. A method as in claim 11, whereinsaid CD-ROM drive couples to the portable computer system via a systembus, and wherein a tri-statable buffer connects said CD-ROM to saidsystem bus.
 13. A portable computer system, comprising: a CPU; a CD-ROMdrive capable of playing an audio CD; a system bus coupling said CD-ROMdrive to said CPU; wherein said CD-ROM drive is isolated from saidsystem bus enabling said CD-ROM drive to remain operable to play theaudio CD while the computer system is in a low-power state.
 14. A systemas in claim 13, wherein said CPU is placed in a low-power state with thecomputer system.
 15. A system as in claim 14, wherein said system buscomprises an IDE bus that also may be placed in a low-power state.
 16. Asystem as in claim 13, further comprising a hard disk drive that couplesvia the system bus to said CPU, and wherein said hard disk drive may beplaced in a low-power state while said CD-ROM drive may be selected toremain in an operational state to play the audio CD.
 17. A system as inclaim 16, further comprising a tri-statable buffer coupled between saidCD-ROM drive and said system bus.
 18. A system as in claim 16, furthercomprising a latch coupled between said CD-ROM drive and said systembus.
 19. A system as in claim 16, wherein said hard disk drive iselectrically isolated from said system bus when in the low-power state.20. A system as in claim 13, wherein the low-power state comprises asuspend mode.
 21. A system as in claim 16, further comprising an audiosubsystem coupled to said CD-ROM, and wherein said audio subsystem maybe selected to remain in an operational state when the CPU and hard diskdrive are placed in a low-power state.
 22. A system as in claim 21,wherein said audio subsystem and said CD-ROM drive remain powered whenan audio CD is played.
 23. A system as in claim 13, wherein the computersystem further includes buttons that are selectable by a user to controlthe playing of an audio CD-ROM in the CD-ROM drive, and wherein saidCD-ROM drive responds to the status of said buttons even when saidcomputer system is in the low-power state.
 24. A system as in claim 13,wherein said audio subsystem comprises a power amplifier.
 25. A systemas in claim 13, wherein said audio subsystem comprises an audio mixer.26. A system as in claim 14, wherein said audio subsystem and saidCD-ROM enter the low power state together with said CPU if no audioCD-ROM is being played.
 27. A system as in claim 14, wherein said audiosubsystem and said CD-ROM join said CPU in the low power state if noaudio CD-ROM is being played.
 28. A portable computer system,comprising: a CPU; a CD-ROM drive capable of playing an audio CD; a harddisk drive; a system bus coupling said CD-ROM drive and said hard diskdrive to said CPU; an isolation buffer coupled between said CD-ROM driveand said hard disk drive to electrically isolate said CD-ROM drive fromsaid system bus; and wherein said hard disk drive may be placed in alow-power state while said CD-ROM drive may be selected to remain in anoperational state to play the audio CD.
 29. A system as in claim 28,wherein said isolation buffer comprises a tri-statable buffer.
 30. Asystem as in claim 29, wherein said tri-statable buffer only couplesbetween said CD-ROM drive and at least one control line of said systembus.
 31. A system as in claim 28, wherein said isolation buffercomprises a latch that couples between said CD-ROM drive and at east onecontrol line of said system bus.
 32. A portable computer system housedin an enclosure, comprising: a CPU; a CD-ROM drive capable of playing anaudio CD; a system bus coupling said CD-ROM drive to said CPU; at leastone button mounted on said enclosure that is selectable by a user tocontrol the playing of an audio CD-ROM in the CD-ROM drive; wherein saidCPU may be placed in a low-power state while said CD-ROM drive may beselected to remain in an operational state to play the audio CD, andfurther wherein said CD-ROM drive reads the status of said at least onebutton when said CPU is in the low-power state.